In petrochemical & refinery plants there are many pipes which are running from source to destination. In most of the cases there is pipe rack between the plant units which carry these pipes and distribute it across the plant. When the pipes are running next to each other there should be some minimum spacing between the pipes so that there shall be no clash between the pipes during construction.

The basic principle for spacing the pipes adjacent to each other is:

Centre to centre between the pipes = half O/D (outside diameter) of the bigger size pipe flange + Insulation thickness of bigger size pipe (if applicable) + 25mm + half O/D (outside diameter) of the smaller size pipe + Insulation thickness of smaller size pipe(if applicable).